MSRA MSRA Data Interpretation 2 — Questions and Answers
Question 1: A study reports a relative risk reduction of 30% for a new drug compared to placebo. The control event rate is 6%. What is the absolute risk reduction?
- 30%
- 6%
- 1.8% (Correct answer)
- 4.2%
Correct answer: 1.8%
Absolute risk reduction = relative risk reduction × control event rate = 0.30 × 6% = 1.8%; the NNT would be 1/0.018 ≈ 56 patients.
Question 2: A new screening test has sensitivity 95% and specificity 80%. In a population with 5% disease prevalence, a patient tests positive. What is the approximate positive predictive value?
- ~20% (Correct answer)
- ~95%
- ~80%
- ~5%
Correct answer: ~20%
In low-prevalence populations, even a test with high sensitivity and specificity yields a low PPV (~20%) because false positives outnumber true positives.
Question 3: A randomised controlled trial reports a p-value of 0.03 and a 95% confidence interval for the mean difference of 0.5 to 4.5 mmHg. What can be concluded?
- The result is statistically significant but clinical significance requires assessment of the effect size (Correct answer)
- The result is not statistically significant
- The confidence interval confirms clinical significance
- The p-value and CI are contradictory
Correct answer: The result is statistically significant but clinical significance requires assessment of the effect size
A p-value <0.05 and CI not crossing zero indicate statistical significance, but whether a 0.5–4.5 mmHg difference is clinically meaningful requires separate evaluation.
Question 4: Urinalysis shows: protein 3+, blood 1+, and microscopy reveals red cell casts. Serum creatinine has doubled in 2 weeks. What does this suggest?
- Urinary tract infection
- Nephrotic syndrome
- Nephritic syndrome with rapidly progressive glomerulonephritis (Correct answer)
- Benign prostatic hypertrophy
Correct answer: Nephritic syndrome with rapidly progressive glomerulonephritis
Red cell casts with haematuria, proteinuria, and rapidly rising creatinine is the hallmark of nephritic syndrome with rapidly progressive glomerulonephritis requiring urgent renal biopsy.
Question 5: A CXR shows bilateral hilar lymphadenopathy, diffuse interstitial shadowing, and no pleural effusion. ACE level is elevated. What is the most likely diagnosis?
- Lymphoma
- Sarcoidosis (Correct answer)
- Pulmonary fibrosis
- Tuberculosis
Correct answer: Sarcoidosis
Bilateral hilar lymphadenopathy with interstitial infiltrates and elevated ACE is the classic radiological and biochemical pattern of pulmonary sarcoidosis.
Question 6: A 24-hour urine collection shows protein 5.8 g/day. Serum albumin is 22 g/L. Cholesterol is 8.2 mmol/L. What syndrome is present?
- Nephritic syndrome
- Chronic kidney disease
- Nephrotic syndrome (Correct answer)
- Rhabdomyolysis
Correct answer: Nephrotic syndrome
The triad of heavy proteinuria (>3.5 g/day), hypoalbuminaemia, and hypercholesterolaemia defines nephrotic syndrome regardless of the underlying glomerulopathy.
MSRA MSRA Data Interpretation 2
A study reports a relative risk reduction of 30% for a new drug compared to placebo.
The control event rate is 6%.
What is the absolute risk reduction?